The kit that I found on Ebay (above) is perfect for the beginner. It's less than $10! It includes a carving tool, some directions, and some Speedball Speedy-Carve. I found a 6X12 sheet of this material for around $10 HERE, just so I could have some extra on hand. The carving material is rubber and somewhat like a pink eraser type material. The carving tool slices through it like butter!
So here's what you do: Decide on an image, maybe simple lines are best for a first try. You can draw directly onto the carving material, or you can print some clip art (like I did). Then gently iron the image onto the rubber material if you do it while the ink is still a little wet. If there are words in your stamp, be sure that they are spelled backwards.
Decide which parts of your stamp are going to be carved out, and mark them as such. It sounds silly, but it can be confusing once you start working in reverse.
Use the carving tool to gently outline the image, then gouge out the interior portions. My carving tool came with two blades, a thick one and a thin one. You can purchase a blade kit once you get a little better at carving.
More in my Letterboxing Series tomorrow!